Add "sample locations" feature to GrProcessor

src/gpu/gl/GrGLProgramDesc.cpp

Index: src/gpu/gl/GrGLProgramDesc.cpp
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index a2dea8739206cbcab2e356ca4e4c4e49da865502..e4ad0b1b089194011b3097284de7b2d9a6427c5b 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -163,6 +163,13 @@ bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
     header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     header->fColorEffectCnt = pipeline.numColorFragmentProcessors();
     header->fCoverageEffectCnt = pipeline.numCoverageFragmentProcessors();
+
+    if (pipeline.hasSampleLocations()) {
+        header->fSamplePatternKey = pipeline.getSamplePatternID();
+    } else {
+        header->fSamplePatternKey = 0;
+    }
+
     glDesc->finalize();
     return true;
 }